Pumping assembly



Decr3, 194 0. R. A. GULICK PUMPING ASSEMBLY Filed Nov. 25, 1939 Patented Dec; 3, 1940 UNITED STATES PUMPING ASSEMBLY Russell A. Gulick, Winthrop, Mass, assignor to Comstock & Wescott,

corporation of Massa Inc., Cambridge, Mass, a chusetts Application November 25, 1939, Serial No. 306,054

5 Claims.

This invention relates to an improved pumping arrangement of the type wherein liquid globules moving through a bore of restricted diameter are effective in pumping and/or compressing successive fluid bodies. More particularly the present invention is applicable to a pump of the drop tube type such, for example, as the purger employed in the low pressure refrigerating system disclosed in the patent to Lyman F. Whitney, No. 2,175,419, dated October 10, 1939.

Systems of this character should operate for a long period of time without necessity for attention and while low absolute pressures are being maintained in their low pressure portions. For example, the operating pressure in the evaporator may be around 4 mm. absolute. When systems of this character have operated with purgers of the type disclosed in the above-identified patent for considerable periods of time, there is sometimes a tendency for an objectionable amount of dirt to collect at the lower or outlet end of the drop tube. Sludge consisting of mercury and refrigerant may also collect objectionably in this region. The present invention more particularly provides an arrangement preventin the objectionable collection of foreign material or dirt at the lower end of the purger tube, and likewise preventing the objectionable collection of sludge in this region.

To permit these desirable results, an arrangement is provided so that a body of the pumped fluid, i. e., non-condensible gases in the case of a purger, may be trapped in a pocket at the lower end of the tube in such a manner that successive liquid globules must pass through this trapped body of fluid before joinin the liquid body surrounding the bottom of the tube. For example, when mercury is employed to provide the liquid globules, successive mercury globules leave the bore of the drop tube in which the globules have acted as liquid pistons. These liquid globules pass through the trapped body offluid, i. e., air or other non-condensible gases, and carry with them small particles of dirt, until they join the body of mercury surrounding the bottom of the tube. Thus the small foreign particles are moved away from the portion of the tube which has a restricted internal diameter. Furthermore, this arrangement results in the trapping of air in such a manner that it ultimately leaves the region of the bottom of the tube in relatively large bodies or bubbles. The resultant agitation of the mercury at the bottom of the tube causes the movement of the foreign particles away from the immediate region of the body of trapped air, thus afiording Fig. 2 is an enlarged vertical sectiona1 detail of the lower part of the assembly shown in Fig. 1; and

Fig. 3 is a section on line 3-3 of Fig. 2, but on a smaller scale.

In general, the accompanying drawing discloses a purger of the type shown in the above-identified patent. Such a purger may form an essential operating part of a refrigerating system such as shown in thatpatent, and may operate over long periods of time to exhaust non-condensible' gases from a system of this character. Such a purger may be provided with an inlet duct I at its upper end for receiving non-condensible gases from the refrigerant condenser of the system. The tube I is arranged to supply these gases to an upper chamber 2, which is provided with a sealing device 3 of the type disclosed in the copending application of Lyman F. Whitney, Se rial No. 136,612, filed April 13, 1937. The flared upper end of a drop tube 5 receives bodies of gas from theupper chamber 2, these bodies being entrapped between mercury globules received from a mercury supply pipe 6. The refrigerating system, for example, may be arranged so that circulating mercury is continually being supplied through the duct 6 to the chamber 2 and the upper end of the drop tube 5.

The tube 5 preferably ma extend downwardly for a substantial distance, so that successive fluid bodies are compressed to a pressure somewhat above atmospheric pressure as these bodies appreach the bottom of the tube. A purger of this character may also conveniently be supplied with a lower chamber or vat Ill surrounding the lower end of the drop tube and adapted to contain a body of mercury having its upper end exposed to the atmosphere, for example through a vent l l.

A return duct l4 preferably is arranged about the drop tube 5 having an open lower end above the lower end of the drop tube. The upper part of the duct It may communicate with a mercury outlet pipe l5 through which the mercury may return to the vaporizer of the refrigerating systern. A purger of this type may also be provided with a deflector [6 of generally cup-like form ex- "tending upwardly about the lower end of the mercury return duct, and arranged to prevent air bubbles from passing upwardly through this duct.

It also may be noted that the flared upper end of the drop tube 5 fits somewhat loosely on the upper part of the return duct l 4, so that the pressures within the chamber 2 and within the upper part of the return duct may be equalized.

In accordance with the present invention, an arrangement is provided at the lower end of the drop tube to prevent objectionable collection of foreign material and sludge at the outlet of the tube, thus to prevent possible clogging of the tube or serious impairment of the operating ef- 15 fectiveness of the pumping assembly. For this purpose the lower end of the tube is preferably provided with an inverted pocket of enlarged cross-sectional area or diameter. The preferred structural arrangement is shown in Figs. 1, 2 and 3 and involves the provision of a separate member 20 fitted onto the lower end of the tube 5 and having aninverted cup-like portion 2| extending downwardly from the lower portion of the body of the tube. The upper part of the member 20 ma be provided with external threads which fit onto an internally screw-threaded portion of the deflector 16. The upper end of the member 29 adjoining the tube 5 and the corresponding portion of the deflector it provide oppositely beveled surfaces between which are washers 23 of compressible material. Accordingly, as the threaded connection between members l6 and 20 is tightened, the material of the washers is forced firmly against the outer surface of the tube 5 so that the members I6 and 20 are thus effectively held in place upon the lower part of the tube. As shown particularly in Figs. 2 and 3, the lower extremity of the return duct i4 may engage the cup-like deflector it, but this end of the duct 40 may be castellated or be provided with notches 24 to permit the movement of mercury in the direction indicated by the small arrows in Fig. 2.

The arrangement of the connection between the members It and 26 and of the washers 23 45 permits the convenient adjustment of the members relative to the tube 5 as well astheir convenient connection thereto and detachment therefrom. Furthermore, this clamping arrangement is effective in preventing upward leakage 50 of gas or air from the inverted pocket into the return duct I 4.

Preferably the member 20 is arranged so that its inner and outer surfaces incline toward each other at the lower extremity of the member,

55 thus for example defining what may be regarded as a thin or sharp annular edge for the wall of the pocket.

In the operation of a pumping device of this character, successive liquid globules such as mer- 60 cury globules entrain bodies of pumped fluid such as bodies of gas in the upper end of the tube 5. As the globules pass downwardly through the tube the gaseous bodies are compressed. When the globules reach the pocket provided by the 65 member 20 they move out of contact with the metal walls, carrying with them any small adhering particles of foreign matter which pass onto or into the body of mercury that affords a liquid surface below the pocketed gas in the 70 member 20. Obviously this surface has an area which is substantially larger than that of the bore of tube 5.

As pumping of the gas continues, the amount of gas in the pocket tends to increase until gas 7 bubbles past the thin, lower edge of the member small bore of the drop tube.

20, thence bubbling upwardly through the mercury body in vat Ill and passing outwardly through the vent II into the atmosphere.

Obviously, as successive mercury globules pass into the body of mercury in the vat, mercury passes from this body upwardly through the return duct M and thence into the duct i5. The bubbling of the air past the lower extremity of the member 2| results in sufficient agitation in this region so that foreign particles and sludge which collect on the mercury surface below the pocket move out of this region and into the large body of mercury in the vat l0. Similarly, this agitation results in the movement of sludge away from the pocket provided by member 25.

The present arrangement is distinctly advantageous in that it avoids wetting of the mercury globules by contact with the mercury body until these globules have moved away from the Consequently for eign particles and sludge move away from the lower end of the drop tube and are then received by the mercury body. As a result, I provide a pump of the class described and specifically an improved purger wherein plugging of the lower endof the drop tube by bodies of foreign materials or by collection of sludge is substantially precluded.

I claim:

1. Drop tube pump comprising a drop tube in which fluid bodies are entrained between liquid globules, a liquid-containing chamber surrounding the outlet end of the tube, said tube having a bore of restricted diameter wherein the globules act as separate liquid pistons, the pump providing an inverted pocket at the lower end of said bore to receive fluid therefrom, said pocket being within the body of liquid in said chamber.

2. A pumping arrangement of the class described comprising a drop tube wherein fluid bodies are entrained between separate liquid globules, a chamber surrounding the lower end of the tube and containing a body of liquid, said tube having a bore of restricted diameter so that the liquid globules may act therein as liquid pistons, an inverted pocket at the lower end of the tube, said pocket having a larger cross-sectional area than said bore and being arranged to contain a body of pumped fluid through which globules may drop free of the adjoining structure and pass into said liquid body.

3. A pumping arrangement of the class described comprising a drop tube wherein fluid bodies are entrained between separate liquid globules which act as liquid pistons, a chamber surrounding the lower end of the tube and containing a body of liquid, and means associated with the lower part of said tube to direct globules therefrom through a trapped body of the pumped fluid before they pass into said liquid body.

4. A pumping arrangement of the class described comprising a drop tube wherein fluid bodies are entrained between separate liquid globules, a chamber surrounding the lower end of the tube and containing a body of liquid, 2. return duct arranged about the drop tube and having a lower open inlet end in said chamber, a deflector between the lower ends of the duct and tube, said tube having a restricted bore so that the liquid globules may act therein as liquid pistons, an inverted pocket at the lower end of the tube having a larger cross-sectional area than said bore, said pocket being arranged to contain a body of pumped fluid through which globules may drop and pass into said liquid body.

5. A pumping arrangement of the class described comprising a drop tube wherein fluid bodies are entrained between separate liquid globules, a chamber surrounding the lower end of the tube and containing a body of liquid, said tube having a restricted bore so that the liquid globules may act therein as liquid pistons, an inverted pocket at the lower end of the tube, said pocket having a larger cross-sectional area than said bore and being arranged to contain a body of pumped fluid through which globules may drop and pass into said liquid body, the pocket having a lower extremity wherein the inner and outer walls are inclined relatively to each other so that the tube has a thin annular edge.

RUSSELL A. GULICK. 

